Field of the Invention
The present invention relates to a light control device, a transparent display device including the light control device, and a method of manufacturing the light control device.
Discussion of the Related Art
Recently, as the society advances to the information-oriented society, the display field of processing and displaying a massive amount of information is rapidly advancing, and correspondingly, various flat panel display (FPD) devices have been developed and are attracting much attention. Examples of the FPD devices include LCD devices, plasma display panel (PDP) devices, field emission display (FED) devices, electroluminescence display (ELD) devices, organic light emitting diode (OLED) display devices, etc.
Recently, display devices are becoming miniaturized, light, and lowered in consumption power, and thus, the application fields of the display devices are continuously increasing. Particularly, in most electronic devices or mobile devices, a display device is used as a type of user interface.
Moreover, transparent display devices which enable a user to look at a background or an object located behind the transparent display devices are being actively researched recently. The transparent display devices are good in space availability, interior, and design and may be applied to various fields. The transparent display devices realize an information recognition function, an information processing function, and an information display function by using a transparent electronic device, thereby solving the spatial limitation and visual limitation of electronic devices. For example, a transparent display device may be applied to windows of buildings or vehicles and thus may be implemented as a smart window which allows a background to be seen or displays an image.
A transparent display device may be implemented as an organic light emitting display device. In this case, power consumption is small, but a contrast ratio is not changed in a dark environment and is reduced in an environment having light. A contrast ratio based on the dark environment may be defined as a dark room contrast ratio, and a contrast ratio based on the environment having light may be defined as a bright room contrast ratio. That is, the transparent display device includes a transmissive area in order for a user to look at a background or an object located behind the transparent display device, and for this reason, the bright room contrast ratio is reduced. Therefore, in a case where the transparent display device is implemented as an organic light emitting display device, a light control device that realizes a light shield mode for blocking light and a transmissive mode for transmitting light is needed for preventing the bright room contrast ratio from being reduced.
Light control devices block most of light in the light shield mode, and for example, may be designed in order for a ratio (hereinafter referred to as a light transmittance) of incident light to output light to be equal to or less than α%. Also, the light control devices transmit most of light in the transmissive mode, and for example, may be designed in order for a light transmittance to be equal to or more than β%. In this case, β is greater than α.
A light control device may be applied to polymer-dispersed LCD devices including liquid crystal and dichroic dyes. In this case, an ultraviolet (UV) curing process of curing a polymer of polymer-dispersed liquid crystal of the light control device is essential. When UV is irradiated onto the dichroic dyes in the UV curing process, the dichroic dyes are discolored, and for this reason, a dichroic ratio (DR) of the dichroic dyes is lowered. The DR may be defined as a long-axis direction absorption ratio of dichroic dyes or a short-axis direction absorption ratio of dichroic dyes. The long-axis direction absorption ratio of dichroic dyes denotes an absorption ratio of light L when dichroic dyes DD are aligned in a long-axis direction Ke as illustrated in FIG. 1A, and the short-axis direction absorption ratio of dichroic dyes denotes an absorption ratio of the light L when the dichroic dyes DD are aligned in a short-axis direction Ko as illustrated in FIG. 1B. As the DR is lowered, a light transmittance becomes higher than a target value “α%” in the light shield mode of the light control device, and for this reason, the light control device cannot normally block light.